diff --git a/math/proof/notes.page b/math/proof/notes.page
index 393343e..f24740f 100644
--- a/math/proof/notes.page
+++ b/math/proof/notes.page
@@ -232,12 +232,12 @@ A_1 \cap A_2 \cap A_3 \cap \dots \cap A_n &=
 Given $A_1, A_2, \dots, A_n$ we define
 
 $$\begin{align}
-\bigcup{i=1}{n} A_i &= A_1 \cup A_2 \cup \dots \cup A_n\\
-\bigcap{i=1}{n} A_i &= A_1 \cap A_2 \cap \dots \cap A_n\\
+\bigcup_{i=1}^{n} A_i &= A_1 \cup A_2 \cup \dots \cup A_n\\
+\bigcap_{i=1}^{n} A_i &= A_1 \cap A_2 \cap \dots \cap A_n\\
 \end{align}$$
 
 $$
-A_1 = \{-1,0,1}, A_2 = \{-2,0,2}, \dots, A_i = \{-i,0,i}, \dots\\
-\bigcup{i=1}{\inf} A_i = \Bbb{Z} \text{ and }
-\bigcap{i=1}{\inf} A_i = \{0\}\\
+A_1 = \{-1,0,1\}, A_2 = \{-2,0,2\}, \dots, A_i = \{-i,0,i\}, \dots\\
+\bigcup_{i=1}^{\inf} A_i = \Bbb{Z} \text{ and }
+\bigcap_{i=1}^{\inf} A_i = \{0\}\\
 $$